This paper reports on a study of teacher support in a setting where students engaged with computer-supported collaborative learning (CSCL) in science. The empirical basis is an intervention study where secondary school students and their teacher performed a lab experiment in genetics supported by a digital learning environment. The analytical focus is on student-teacher interactions taking place in help-seeking settings during group-based activities where students analysed and reported their findings from the lab experiment. A combination of quantitative methods in the form of frequency counts of students' help requests and detailed micro-analyses of student-teacher interactions are used. The findings are that the majority of challenges faced by students concerned conceptually oriented issues and procedural challenges in the sense of how to practically solve the assignments provided to them in the digital learning environment. Most importantly, the analyses of student-teacher interactions provide insight into the considerable amount of support that is needed from the teacher to bridge the conceptual gap between the lab experiment and the students' understanding of the underlying scientific principles and procedures. The findings are discussed according to possible implications for the design of digital support tools and instruction.